1. Field of Invention
The present invention relates to systems, processes and products for determining the phase of the menstrual cycle and particularly to measurement of transparency and/or diffusivity of bodily mucus, particularly cervical and/or oral mucus in order to predict and to indicate the inception and the presence of ovulation for conception control.
2. Description of the Prior Art
It has been found that mucus sampled from the vaginal and oral cavities undergoes distinct physical and chemical changes during the menstrual cycle. For example, cervical mucus, a hormonally controlled secretion, is produced continuously, varying in quantity, composition and physical properties during the menstrual cycle. In the cervical canal, the anatomic connection between the vaginal lumen and the uterine cavity, the mucus secreted by the cervical glands acts as a mechanical and biochemical barrier against intruding organisms, including male spermatozoa. During the preovulatory phase, under estrogen domination, the mucus is profuse, watery, optically clear, alkaline and favorable to sperm penetration. During the postovulatory, progestational phase, the mucus changes remarkably becoming less abundant and fluid, more optically opaque, and less alkaline or slightly acidic. During this phase, the cervical mucus, which contains an increased number of leukocytes and other cellular components, is practically impenetrable to spermatozoa. In healthy women with normal menstrual cycles, as is well documented in the medical literature, ovulation usually occurs between the 12th and 14th day prior to the next menstrual period. Determining ovulation on the basis of the preceeding menstrual period, such as in the rhythm method of counting the days ellapsed between the termination of the menstrual period and the presumed mid-cycle ovulatory phase, is prone to errors because of the great variability in the length of the proliferative period, i.e. between the end of the menses and ovulation. Although it is possible to predict ovulation on the basis of hormonal changes in the blood or chemical changes in the mucus, present procedures for analyzing such changes are useful only in special cases, because of the laboratory time and high cost required to perform analyses, which may take from several days to two weeks. By the time the results are available to the gynecologist, about half of the menstrual cycle may have elapsed. At the present time, there are no known reliable on-the-spot techniques capable of providing the information necessary for prediction or confirmation of ovulation during or immediately after examination of a patient.
It is known also that several optical properties of cervical mucus change considerably during the menstrual cycle. These properties include index of refraction, transparency (transmittance) to white light and to light of selected wavelengths, and diffusivity. The most important single factor determining the degree of transparency of mucus is water concentration. The mucus is most hydrated at the time of ovulation, containing 97 to 98% water. At other times during the menstrual cycle, the mucus is relatively dehydrated, containing only 80 to 90% water. The solids or non-volatile residue remaining in the mucus after desiccation may range from 2% to 20% of the weight of fresh mucus, representing as much as a 10 fold increase between the time of ovulation and other periods in the cycle. The solid residue consists primarily of proteins, salts, carbohydrates, lipids, exfoliated cellular elements and other organic materials, such as bacteria. The major mucus fraction is a carbohydrate rich glycoprotein, which accounts for 70 to 80% of the dry residue. The remaining fraction essentially includes 20 to 30% aminoacid residues, as well as sodium chloride and other inorganic salts. Protein concentration varies considerably during the menstrual cycle, ranging from about 40 to 50 mg per gram of total weight during the proliferative and luteal phases to about 3.5 mg per gram of total weight at ovulation. Electron-microscopic studies of cervical mucus show that, at mid-cycle, mucus consists primarily of clusters of globular particles, 1000 to 1500 A in diameter, connected by thin string-like strands of material. In the early luteal phase, these mucus strands are considerably enlarged to about 200 A in diameter, creating an interlocking mesh without spherical components. It is believed that the change in structure that accompanies decrease in protein concentration at mid-cycle, coupled with an increase in water, renders the mucus transparent at that time. At the other times during the menstrual cycle, the mucus becomes increasingly opaque as a function of the concentration of proteins and cellular debris. A need has arisen for improvements in devices and processes which utilize the foregoing for the purpose of determining ovulation.